Now to get the full story, do you have to read every single one of those extra comic books, or can you just read the main mini series?

One thing I've never liked about comics is that you have to read books outside of the specific series you might be interested in and it becomes a complete mess. How would you even figure it out if you didn't have the internet?

AvX wasn't that amazing to begin with so its definitely not necessary to read the tie-ins. I read all the tie-ins for Civil War, but that was a much bigger event. I'd probably do the same if i read Fear Itself. But AvX was relatively small despite the major outcome.